Chapter 3 Metals and Non-metals

Metals generally do not show dullness. Metals such as gold and silver usually are shiny rather than dull.

The ability of metals to be drawn into thin wire is called ductility. It is one such property of metals that is used to make wires from metals. Metals such as copper have high ductility and thus can be drawn into long and thin wires without breaking.

Aluminium has good thermal conductivity and high melting point. As a good conductor of heat, it helps in heat transfer and cooking of food. With the high melting point, one can cook food in such utensils at higher temperatures and the aluminium utensils can withstand such higher temperatures without being melted by the heat.

Na (sodium) and Ca(calcium) react with water vigorously. Mg (Magnesium) reacts with water less vigorously than that of calcium and sodium. Fe (Iron), on the other hand, does not react with cold as well as hot water instantly. But when the iron is kept in contact with water for a long time, rusting of iron happens.

When steam is passed over iron for a long time, it gives iron oxide (Fe₃O₄) and hydrogen gas.

3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g)

When calcium is treated with water, it reacts with water vigorously and to produce a cloudy white precipitate of calcium hydroxide and hydrogen gas is released as bubbles.

Ca(s) + 2 H₂O(g) → Ca(OH)₂(s) + H₂(g)

Sometimes hydrogen bubbles get stuck to the surface of calcium metal making it light and thus calcium starts floating. This reaction is exothermic in nature.

does not give hydrogen gas on reacting with metals. Nitric acid is a strong oxidizing agent. It oxidizes hydrogen produced in the reaction to water and nitric acid itself is reduced to any of these nitrogen oxides [N₂O (nitrous oxide), NO (nitric oxide) or NO₂ (nitrogen dioxide)]. On the contrary, magnesium and manganese reacts with dilute nitric acid to give salt and hydrogen gas.

Aqua-regia is a mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1. Aqua-regia being a very strong acid dissolves gold in it.

Non-ionic compounds are those that have covalent bonds. Hydrochloric acid (HCl) and carbon tetrachloride (CCl₄) form covalent due to sharing of a pair of electrons between two atoms. Whereas sodium chloride (NaCl) and potassium chloride (KCl) form ionic compounds as they consist of positive and negative ions.

In solid state, ions in ionic compounds are not free to move. Thus, such compounds do not show electrical conductivity in solid state. Whereas, in molten state, ions are free to move and hence conduct electricity.

Gold (Au) and silver (Ag) are not reactive or very less reactive. These metals are called noble metals. Thus, these are placed at the bottom of the reactivity series. Since gold and silver are least reactive of all the metals, these are found in free state in nature.

Gold (Ag) and copper (Cu) obtained after extraction is in impure form. So, metals Au (gold) and Cu (copper) are refined by electrolytic refining. Other than gold and copper, electrolytic refining is used for metals such as Zn and Ag. Sodium (Na) and potassium (K) are extracted by electrolytic reduction. Metals obtained after electrolytic reduction are in pure form.

Silver articles turn black after prolonged exposure to air due to the reaction of sulphur present in air. Silver reacts with sulphur to form dark grey to black silver sulphide.

Coating iron or steel with a layer of zinc prevents it from rusting. This process is called galvanization. Water pipes are also galvanized to protect them from corrosion.

Alloying elements enhance the structure and properties such as durability, strength and toughness of the metal. It makes them corrosion resistant. Stainless steel is an alloy of iron, nickel and chromium.

Copper gets green coating due to the formation of a mixture of copper carbonate and copper hydroxide when it reacts with carbon dioxide gas and moisture present in air. This is called tarnishing of copper.

The reactionn is as follows:
2Cu + H₂O + CO₂ + O₂ → Cu(OH)₂ + CuCO₃

Mercury (Hg) is the only metal which is found in liquid state at room temperature. All other metals are solid at room temperature. It also has the lowest melting point.

Sodium and calcium are very reactive metals and are placed towards the top of the reactivity series. These are produced by the electrolysis of their molten chlorides. The metal ions are deposited at negatively charged cathode and chlorine is deposited at positively charged anode.

Iodine is a non-metal that is lustrous. Graphite is another non-metal that is shiny and lustrous.

Ag (silver) would be displaced from the solution of its salts by other three metals, i.e., magnesium (Mg), zinc (Zn) and copper (Cu). Silver (Ag) is a noble metal and is least reactive metal among other metals given.

Explanation: Test tube C contains chemical mixture called aqua-regia. It is a mixture of concentrated HCl and concentrated HNO₃ in the ratio of 3:1. Aqua-regia dissolves gold and platinum in it while hydrochloric acid and nitric acid do not.

An alloy is a homogeneous mixture. Alloy is a homogeneous mixture of two or more metals. For example, brass is an alloy of copper and zinc. Stainless steel is an alloy made with combination of iron with chromium with nickel.

An electrolytic cell consists of positively charged anode and negatively charged cathode. Positively charged ions (cations) are deposited at negatively charged cathode. Negatively charged ions (anions) are deposited at positively charged anode.

During electrolytic refining of zinc, it gets deposited on cathode. Since, zinc ions are positively charged, it gets deposited at the negatively charged cathode.

Na (sodium) possesses all the above properties. It is too soft and can be cut with a knife. It is also very reactive and reacts with oxygen or moisture present in air and produce sodium hydroxide which is highly exothermic reaction producing a lot of heat. It also reacts with water vigorously and burns due to the formation of hydrogen gas. That is why sodium is stored in kerosene oil to prevent any reaction.

Steel contains non-metal as one of its constituents. Steel is an alloy made by combining iron and other elements mainly carbon. Carbon gives strength to iron. It is used to make buildings, ships, automobiles, machines, appliances.

Magnesium metal reacts with cold water to form magnesium oxide and evolves hydrogen gas is an incorrect statement. Magnesium when reacts with water gives magnesium hydroxide and hydrogen gas. Reaction of metals and water generally produce hydrogen gas and their respective hydroxide. For example, sodium metal reacts with water to produce sodium hydroxide and liberates hydrogen gas.

Zinc amalgam contains mercury as one of its constituents. An alloy of mercury with another metal is called amalgam. Almost all metals except iron, platinum, tungsten, and tantalum can form amalgams with mercury. Amalgams of silver and mercury are important in dentistry. Amalgams of gold and mercury are used in the extraction of gold from its ore.

Stainless steel: An alloy of Fe and C

Alnico: An alloy of Al, Ni and Co

Solder: An alloy of Pb and Sn

Compound Z does not show the property of “Has low melting point”. As compound Z is formed because of transfer of electrons between X and Y, hence Z is an ionic compound. Such compounds do not have low melting point. Bonds in ionic compounds are very strong. Therefore, a lot of energy is needed to break them. This is the reason why ionic compounds have high melting and boiling points.

Atomic number of X is 10, so this must be Ne (Neon), a noble or inert gas. This gas has octate configuration.

Atomic number of Y is 2 + 8 + 7 = 17, so this must be chlorine (Cl). Chlorine is a non–metal. Non-metals have 5 to 7 electrons in their valence shell.

Atomic number of Z is 2 + 8 + 2 = 12, so this must be Magnesium (Mg). Magnesium is a metal. Metals have 1 or 2 electrons in their valence shell.

Al (aluminium) forms amphoteric oxides. An amphoteric oxide acts both as an acid and as a base.

Graphite is a good conductor of electricity and heat. Graphite has weak intermolecular forces between its layers. Hence it has de-localised electrons. As electrons are free to move through its structure, it conducts heat and electricity well.

Electrical wires have a coating of an insulting material called PVC (Polyvinylcloride). PVC is a polymer and bad conductor of electricity. It is the most common insulating material used to insulate electrical conductors from electric charge thus preventing human contact with live electricity.

Graphite is good conductor of electricity. Hence it cannot be used as insulating material.

Sulphur, although is a bad conductor of electricity, but is brittle in nature. So, cannot be used as insulating material.

Bromine, a non-metal, is a liquid. Metals are generally solid whereas non-metals can be solid, liquid and gas. Bromine is a non-metal that exists as liquid.

CuSO4 + Fe can undergo a chemical reaction. As iron metal is more reactive than copper metal, iron displaces copper from copper sulphate solution and forms aqueous iron sulphate (FeSO4) and solid copper (Cu). This a single displacement reaction also known as a substitution reaction. The iron can be solid or aqueous but the copper sulphate must be aqueous in order to facilitate the reaction.

Figure (c) correctly describes the process of electrolytic refining.

In the process of electrolytic refining, impure metal (calcium) forms the positively charged anode whereas pure metal forms the negatively cathode. Copper sulphate (CuSO₄) is taken as an electrolyte.

Figure (c) shows the process of electrolytic refining of copper metal. Copper from impure anode dissolves into the solution. Copper ions (Cu²⁺) from the solution are deposited on the cathode.

The lustrous, divalent element must be a metal. Metals that are very reactive reacts with sodium hydroxide readily and bubbles are produced due to formation of hydrogen gas. When a burning candle is brought near the reaction vessel, a pop sound is produced.

(a) Impure silver is taken as anode. Pure silver is taken as cathode.

(b) Suitable electrolyte is any silver salt such as AgNO₃.

(c) We get pure silver at cathode.

In the process of electrolytic refining of silver, impure metal (impure silver) forms the positively charged anode whereas pure metal (pure silver) forms the negatively cathode. Silver nitrate (AgNO₃) is taken as an electrolyte. Silver from impure anode dissolves into the solution. Silver ions from the solution are deposited on the cathode.

Extraction of a metal from its oxide is easier as compared to its extraction from its sulphides and carbonates. Metals occur in the form of its ores. An ore is a mineral from which metal can be extracted. Ores found in the form of carbonates and sulphides are first converted into their oxides by the process of calcination and roasting. Oxides thus obtained are converted to metals by the process of reduction. Later metals are purified by various purification methods.

Nitric acid (HNO₃) is a strong oxidising agent. When a metal reacts with dilute nitric acid hydrogen gas is released. Nitric acid oxidises the hydrogen (H₂) to water (H₂O) and itself gets reduced to NO₂ or NO or N₂O. So, no hydrogen gas is evolved in this case.

(a) X is Fe₂O₃.

(b) The name of the reaction is thermite reaction. This is a redox reaction between aluminium and iron (III) oxide that produces molten iron as aluminium is more reactive metal than iron. This reaction is highly exothermic and heat is produced.

(c) Fe₂O₃(s) + 2Al(s) →2Fe(l) + Al₂O₃(s) + Heat

X is Na , Y is NaOH and Z is H₂

The reaction is : 2Na + 2H₂O→ 2NaOH + H₂ + Heat Energy

Since the molecular formula of Y = XOH, let’s suppose the atomic weight of metal X is a. Then, molecular mass of XOH = a + 16 + 1 = 400.

Then, a = 40 – 17 = 23. The atomic weight of sodium is 23, so metal X is sodium (Na). Sodium reacts with water to give hydrogen gas (Z) that catches fire.

So, metal X is sodium (Na), Y is (sodium hydroxide) and Z is H₂ (hydrogen gas).

Here, X is Carbon, Y is Diamond Z is Graphite.

Non-metal X is carbon (C). Carbon exists in two different forms. These different forms of carbon are called the allotropes of carbon. Diamond and graphite are allotropes of carbon.
Y is diamond because diamond is the hardest natural substance. Z is graphite as it is a good conductor of electricity.

(a) No, aluminium is getting oxidized as oxygen is added to it to form aluminium oxide.

(b) No, manganese is getting reduced as it has lost its oxygen.

Since aluminium is more reactive than manganese, it displaces manganese from its oxide. Aluminum accepts oxygen from manganese dioxide. It reduces the manganese dioxide to manganese and aluminum oxide is formed.

Solder is an alloy made from the combination of lead and tin. It is used for welding electric wires because it has a low melting point.

The metal A is Aluminum , B is Al₂O₃

The reaction is:
Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O
Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O

Metal A is aluminium (Al) that is used in the thermite process. Al reacts with oxygen to form aluminium oxide [Al₂O₃ (B)], which is amphoteric in nature. Thus, aluminium oxide reacts both as a base and as an acid.

Mercury is the only metal that exists as liquid at room temperature. It is placed low in reactivity series and can be obtained by reducing their sulphides or oxides by heating. It can be obtained by heating the sulphide ore of mercury called cinnabar (HgS).

The reactions are as follows:
2HgS + 3O₂ → 2HgO + 2SO₂
2HgO → 2Hg + 0

A formulae is the representation of compounds in terms of symbols of its various elements.

(a) Mg and N₂ reacts to formMg₃N₂ (magnesium nitrate).

(b) Li and O₂ reacts to formLi₂O (lithium dioxide).

(c) Li and O₂ reacts to formAlCl₃ (aluminium chloride).

(d) K and O₂ reacts to formK₂O (potassium oxide).

(a) When zinc carbonate is heated in the absence of oxygen, zinc oxide and carbon dioxide are produced. The process of reduction carbonate ores to form oxides in absence of oxygen is called calcination. Zinc is found in its ore – zinc carbonate. When this ore is heated, zinc oxide is formed along with carbon dioxide.

ZnCO₃ → ZnO + CO₂

(b) When a mixture of copper oxide and copper sulphide is heated, pure copper is obtained. It undergoes auto reduction. When sulphide ore of copper is heated, a part of this ore is converted into oxide which then reacts with remaining sulphide ore to give pure copper and sulphur dioxide.

2Cu₂O + Cu₂S → 6Cu + S

(a) A is carbon (C) as it is an important constituent of our food , B is carbon monoxide (CO) as it is highly poisonous and toxic and C is carbon dioxide (CO₂) as it is the main cause of global warming.

(b) A belongs to Group 14 of the periodic table. It has atomic number 6. Its electronic configuration is 2, 4.

Metals in general, are conductors of heat. Some are good conductors whereas some are poor conductors of heat. Owing to the number of free electrons they have, they are classified into good or poor conductors of heat. Those metals that have more number of free electrons are good conductors and those that have less number of free electrons are poor conductors of heat.

(a) Ag (Silver) and Cu (Copper) are good conductors of heat.

(b) Pb (Lead) and Hg (Mercury) are poor conductors of heat.

A metal that exits in liquid state at room temperature is mercury (Hg). A non-metal that exits in liquid state at room temperature is bromine (Br).

Two metals with melting points less than 310K (37°C) are Cesium (Cs) and Gallium (Ga).

A is Ca, B is Ca(OH)₂ , C is CaO
Ca(s) + 2H₂O → Ca(OH)₂ + H₂ (g)
Ca(OH)₂ → CaO + H₂O

Element A is calcium (Ca). When calcium reacts with water, it forms calcium hydroxide [Ca(OH)2]. Calcium hydroxide is used in white washing. Thus compound B is calcium hydroxide [Ca(OH)2]. Compound B on heating gives oxide of calcium (CaO). Thus, C is calcium oxide (CaO). Calcium oxide (CaO) on treatment with water gives back B [Ca(OH)2].

A is Na, B is NaOH, C is NaAlO₂
2Na (s) + 2H₂O → NaOH+ H₂ (g)
Al₂O₃ + is NaOH → 2NaAlO₂ + H₂O

Let ‘s suppose the atomic weight of alkali metal A be x. When it reacts with water, it forms a compound B having molecular mass 40.

Therefore, x + 16 + 1 = 40
x = 40 –17 = 23
The atomic weight of Na (sodium) is 23.
Therefore, the alkali metal (A) is Na. Sodium reacts with water to form sodium hydroxide. So, compound B is sodium hydroxide (NaOH).
Sodium hydroxide reacts with aluminium oxide (Al₂O₃) to give sodium aluminate (NaAlO₂). Thus, C is sodium aluminate (NaAlO₂).

(a) 2ZnS (s) + 3O₂→ 2ZnO+ 2SO₂ (g)
(b) ZnCO₃ (s) → ZnO (s) + CO₂ (g)

Zinc is commonly extracted from its ore called zinc blende also known as zinc sulphide (ZnS). Firstly, froth flotation process removes gangue from sulphide ores. During roasting, the concentrated ore is finely ground and made to react with a stream of air. This converts zinc blende to zinc oxide (ZnO) which is more reactive. During calcination, the carbonate ore is heated strongly in the absence of air to convert it into metal oxide.

The metal M is Cu and the black coloured product is copper oxide (CuO). Copper does not react with acids but reacts with oxygen to form copper oxide. The reaction of metal M with oxygen is as follows:

2Cu + O₂→ 2CuO

Non-metallic oxides are acidic in nature. Therefore, A is a non-metal.

We know that iron is more reactive than copper. Hence, iron displaced copper from copper sulphate solution. This reaction is called displacement reaction. Due to displacement, there is formation of holes in the iron pot. The following equation shows this reaction.

CuSO₄ + Fe → FeSO₄ + Cu

The non-metal A is nitrogen (N₂). It forms the largest constituent of air, i.e., 78%. When N₂ is heated with H₂ in 1:3 ratio in presence of iron (Fe) as catalyst, it forms ammonia gas (NH₃). This is known as Haber process. Thus the gas B is ammonia. When ammonia is heated with O₂, it forms nitric oxide (NO). NO further gets oxidized to NO₂ by O₂. Thus, oxide C is NO₂ (nitrogen dioxide). When this oxide reacts with water in the presence of air (O₂), it gives nitric acid. Thus acid D is nitric acid which is a strong oxidizing agent. The chemical reactions involved are as follows:

N₂(g)+3H₂(g)→2NH₃(g)

4NH₃(g)+5O₂(g) 4NO(g)+6H₂O(g)

2NO(g)+O₂(g)→2NO₂(g)

4NH₂+2N₂O+O₂→4HNO₃

(b) Nitrogen belongs to Group 15 of periodic table because nitrogen has 5 valence electrons (electronic configuration is of N is 2, 5).

Extraction of metals of low reactivity: Mercury is a less reactive metal. The ore of mercury is called cinnabar, i.e. mercury (II) sulphide. The ore is heated in air and is oxidized to produce mercury (II) oxide. Mercury oxide is reduced to obtain mercury. The following reactions are involved in this process.

2HgS + 3O₂→ 2HgO + 2SO₂

Extraction of metals of medium reactivity: The metals in the middle of the reactivity series are also extracted by roasting followed by the process of reduction but the methods are somewhat different. Let’s take the example of zinc.

Extraction of Zinc: Zinc is placed in the middle of the reactivity series. It occurs as zinc blende (zinc oxide). It is first heated in the presence of air to obtain zinc oxide. This process is shown by following equation:

2ZnS + 3O₂→ 2ZnO + 2SO₂

After that, zinc oxide is reduced to obtain pure zinc metal. The reduction is done in the presence of carbon. This can be shown by following equation.

ZnO + C Zn + CO

(a) When aluminium (Al) is dipped in nitric acid (HNO₃), a layer of aluminium oxide is formed on the metal. This happens because nitric acid is a strong oxidizing agent. The layer of aluminium oxide prevents further reaction of aluminium. This is the reason why the reactivity of aluminium decreases.

(b) Sodium and magnesium have tendency to react with oxygen rather than carbon because these are highly reactive metals. Hence, carbon cannot reduce the oxides of Na or Mg.

(c) Ionic compounds do not conduct electricity in solid state but they conduct electricity in aqueous solution and in molten state due to high concentration of free electrons. This property is shown by sodium chloride as it is an ionic compound.

(d) Iron articles are galvanized to prevent them from rusting. After galvanization, the layer of zinc works as protective layer. The most common type is hot-dip galvanizing. In this process, iron parts are submerged in a bath of molten zinc.

(e) Metals such as Na, K, Ca and Mg are highly reactive metals and hence they are not found in their free state in nature.

(a)2Cu₂S + 3O₂→ 2Cu₂O + 2SO₂

(b) 2Cu₂O + Cu₂S → 6Cu + SO₂

(c) At cathode: Cu²⁺ + 2e⁻→ Cu

(ii)

Metal X is sodium. Metal Y is magnesium. Metal Z is iron.

Order in reactivity series: Na > Mg > Fe

Element A is sodium that burns with golden flame. Element B is chlorine. Its atomic number is 17. Product C is sodium chloride. Compound D is sodium hydroxide. When sodium reacts with chlorine, it gives sodium chloride.

Na + Cl → NaCl

Electrolysis of sodium chloride gives sodium hydroxide.

2NaCl + 2H₂O → 2NaOH + Cl₂ + H₂

When carbonate ore (ore A) is heated, it produces carbon dioxide. A carbonate ore undergoes calcination to give metal oxide. For example, zinc carbonate undergoes calcination to give zinc oxide.

ZnCO₃ → ZnO + CO₂

When a sulphide ore (ore B) is heated, it produces sulphur dioxide. A sulphide ore undergoes roasting to give metal oxide. For example, zinc sulphide undergoes roasting to give zinc oxide.

2ZnS + 3O₂→ 2ZnO + 2SO₂

After calcination or roasting, zinc oxide should be reduced to obtain zinc. ZnO is a white powdery substance and is insoluble in water.

2ZnO + C → 2Zn + CO₂